Nanotubes: The Next Asbestos?

The story of asbestos in this country ought to serve as a cautionary tale: A seemingly miraculous fiber was widely introduced into common consumer products; only after it was already in millions of homes did the general public realize that it causes a particularly terrible form of cancer. Now, treating victims and cleaning up contaminated communities is costing billions of dollars, while thousands of people endure the toll of a debilitating and deadly disease.

Nanotechnology is another innovation that promises to bring consumer products to a whole new level – and, once again, it looks like nano products will become widespread and entrenched before we have a complete picture of what the risks are.

Nanotechnology involves extremely small particles measuring 1 – 100 nanometers (down to 1/100,000th the width of a human hair). This gives the particles more surface area relative to their weight, which can make them more reactive and change their properties in other ways. Such changes can offer new opportunities, but they can also pose dangers. In fact, a pilot study published in the latest issue of Nature Nanotechnology suggests that carbon nanotubes behave like asbestos, causing mesothelioma-like lesions in the body.

Carbon nanotubes have distinctive characteristics, but their needle-like fibre shape has been compared to asbestos, raising concerns that widespread use of carbon nanotubes may lead to mesothelioma, cancer of the lining of the lungs caused by exposure to asbestos. Here we show that exposing the mesothelial lining of the body cavity of mice, as a surrogate for the mesothelial lining of the chest cavity, to long multiwalled carbon nanotubes results in asbestos-like, length-dependent, pathogenic behaviour. This includes inflammation and the formation of lesions known as granulomas. This is of considerable importance, because research and business communities continue to invest heavily in carbon nanotubes for a wide range of products under the assumption that they are no more hazardous than graphite. Our results suggest the need for further research and great caution before introducing such products into the market if long-term harm is to be avoided.

There are the usual caveats about making any sweeping assumptions based on this: it’s one short pilot study, done on mice, and the nanotubes were injected directly into the body, which is not how most of us would be exposed to the fibers. What it does tell us is that we ought to slow down and quit pumping these fibers into workplaces and the marketplace until we know more.

Carbon nanotubes are already used in dozens of products, including electronic components, tennis rackets, and golf clubs, and the Washington Post’s Rick Weiss states that they’re expected to be a $2 billion industry within the next few years. Kenneth Chang’s New York Times article suggests that consumers aren’t likely to inhale nanotubes from bicycle frames, but cites one of the study authors cautioning that workers may be at more of a risk, just as construction workers and mechanics have a higher risk of asbestos exposure.

Regulating nanotechnology is challenging, because we’re not exactly sure how fibers of different sizes will behave. Even in this mouse study, shorter nanotubes didn’t cause lesions, while longer ones did.

Plus, when considering the nanotechnology field as a whole, there are several different fibers. In addition to the carbon nanotubes, nano particles of silver are widely used to give products antimicrobial properties. As Carole Bass pointed out in The New Republic earlier this month, spreading nano-silver particles far and wide could have serious consequences for the environment as well as for individuals – for instance, the bacteria we rely on to clean our water and perform other services might suffer. This means that the FDA and EPA will both need to be involved.

“We’ve got to have the right research, and really fast,” nanotube study author Andrew Maynard of the Project on Emerging Nanotechnologies told the Washington Post. But the question is, will we get the right research and put it to use quickly, or will the companies that make and use nanotubes gum up the process?

Like tobacco companies, the companies that made and used asbestos denied that there were problems with the substance long after they knew about the diseases it caused. (I’ll put in a quick plug for David Michaels’s Doubt is Their Product; Chapter 2 of the book tells the sordid asbestos story, and we’ve put related documentary evidence online.) Let’s hope that the companies using carbon nanotubes don’t stand in the way of regulating a substance that has the potential to cause another asbestos-type public health crisis.

8 comments

This story has popped up half a dozen times, and I have commented on most of them.

Carbon nanotubes are just high-tech carbon black. Likely more potent because of smaller particle size, so more particles per gram, and more surface area because of structure. Carbon black is an IARC Group 2B carcinogen, based on sufficient evidence in laboratory studies. It would be a surprise to most toxicologists if the same result were not found for carbon nanotubes.

Carbon nanotubes behave the same as carbon black in short term assays for lung inflammation.

I’m doubtful a ban on carbon black is feasible. So there’s a need for a reference concentration for carbon black, ultrafine carbon black, and carbon nanotubes. Less than unlikely in this administration.

The emphasis on consumer products I think is quite a red herring. As indicated, these products will result in exposures in manufacture and potentially in disposal. But in terms of risk and volumes the use of carbon nanotubes as a routine additive to concrete is a bigger concern. Retention of the asbestos-mimicking fibrous structure is necessary to the function – crossing voids in the concrete matrix – and will result in construction worker exposures (and incidental exposures) in those using and machining concrete. We already know this is a dusty job, and you can add nanotubes to silica, chromium, silica and other cancer risks already present in dust from good, old-fashioned concrete.

Nanoparticles are more than just tiny dust. Elder et al (Translocation of Inhaled Ultrafine Manganese Oxide Particles to the Central nervous System; Environmental Health Perspectives 114 (8) 1172-1178 August 2006) showed that they are small enough to be taken up by the neurons of the olfactory nerve (the one you use to smell). Although studies haven’t been done showing further migration within the brain, it is commonly accepted that this is the route used for herpes virus to gain access to the brain when causing herpes encephalitis. Although not as devastating as herpes, the pathway from the olfactory nerve to the temporal lobe could easily be traversed by nanoparticles and the temporal lobe is the locus for most uncontrolled forms of epilepsy. A foreign substance and the inflammation it causes would easily cause serious seizures in the temporal lobe. This research used MnO particles. I don’t know if the same studies have been done with carbon.

Since there is no money to be made from publishing a list of safe materials, nobody will do it.
Until then, we must all listen and read about speculation and extrapolation and whatever -ation puts money in the pockets of researchers and regulation agencies.

When it comes to health we do the best we can with what we know. It’s just scary how little we sometimes know. We understand very little about the long term consequences of prescription drugs etc. We just do the best we can with what we know. What else can we do? Our health is the most important thing in our life. If your job is endangering your health you should avoid that type of employment. It Didn’t matter how much money you make at the job your health is priceless.